Small C++ program to display images in a (modern) terminal using RGB ANSI codes
and unicode block graphic characters.

There are various similar tools (such as timg) using the unicode half block
character to display two 24bit pixels per character cell. This program enhances
the resolution by mapping 4x8 pixel cells to different unicode characters,
using the following algorithm:

For each 4x8 pixel cell of the (potentially downscaled) image:
* Find the color channel (R, G or B) that has the biggest range of values for
  the current cell.
* Split this range in the middle and create a corresponding bitmap for the cell.
* Compare the bitmap to the assumed bitmaps for various unicode block graphics
  characters.
* Re-calculate the foreground and background colors for the chosen character.